Re: Suggestions for first exam ...

"Anurag Varma" <avdbi_at_hotmail.com> wrote in message news:H5Qdb.3038$6y3.1848_at_news01.roc.ny...
>
> "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message
 news:bl61qb$mec$1$8302bc10_at_news.demon.co.uk...
> --snip--
> > "Richard Foote" <richard.foote_at_bigpond.com> wrote in message
> > news:rGgdb.126227$bo1.111770_at_news-server.bigpond.net.au...
> > >
> > > Coincidently again (first the last time), I've noticed a new article
 by
> > > Jonathan Lewis at dbazine which nicely describes why the unbalanced
 Oracle
> > > index is myth of utter crappy proportions (perhaps my complaint had
 an
> > > effect ?)
> > >
> >
> > I wrote it because I came across yet another bloody
> > "expert" explaining that sequences cause Oracle's
> > indexes to get extremely deep on the right so that
> > indexes need to be rebuilt.
> >
> > There is another article coming out soon (I think)
> > that points out why it is usually a waste of time
> > to rebuild indexes at all - and gives an example
> > showing how a regular rebuild can make things
> > worse.
>
>
> The article by Mike Hordila is published in oracle own site:
> http://www.oracle.com/oramag/webcolumns/2001/index.html?auto_index.html
>
> Now how does Oracle itself let this guy publish (in their own website) a
 totally untrue article showing the ;) fascinating
> diagram of what unbalanced indexes look like.
>
> :)
> In fact you should see his site http://members.rogers.com/mhordila/
> he's got loads of useless and myth creating articles out there.

Which appears to have the answer to your question Anurag

" My article entitled "Automated Index-Rebuilding System"

(Oracle Magazine Online, September 2001) shows

a drawing representing an unbalanced index. The Oracle

manuals, and also Oracle note 30405.1, state that

indexes are always balanced because "the definition of a

Balanced Tree is that all the data is on the same level."

This is a nice theoretical concept, however, I am more a

practical person than a theoretician, and I think that this

type of balance is difficult to implement perfectly, and a

number of practical imbalances can arise. Exhibit 5

shows how an index grows its depth. "

Perhaps the magazine editors are "practical people" as well and think that the the documented behaviour is wrong. Being not *very* practical people they can't be expected to test their opinion.

-- 
Niall Litchfield
Oracle DBA
Audit Commission UK